Description Need help? Here’s a quick lesson on automotive exhaust pipe sizing. – Components such as mufflers, catalytic converters and resonators are generally measured in I.D. sizes. – Pipes such as extension pipes and tail pipes are measured in O.D. sizes. Although both part types possess the same advertised diameter, pipes are meant to slide into components. 548630, 548631, 548632, 548633, 548634, 548635, 548636
